Contact material



a t nee. 4, 1934 i 1,982,812

oon mcr MATERIAL Charles V. Iredell, East Orange, N. .L, assignor to Westinghouse Lamp Company, a corporation of Pennsylvania 'I No Drawing. Application September 2, 1931,

Serial No. 560,863

1 Claim. (Cl. 200-166) This invention relates to electrical contacts the below described manner has been found to and is more particularly directed to means of have excellent heavy electrical duty characterthis character especially adapted for use in istics. high duty electrical service devices, as for ex- Among others, some of the more essential 5 ample, heavy relays, motor starters, circuit properties of my novel contact means are asbreakers, short circuit switches and the like. follows: its composition is such that it may be Contact means heretofore commercially promanufactured at a minimum cost in units of subduced and employed in high duty electrical destantially uniform and unvarying dimensions; it vices have not been entirely satisfactory because will not promote ionization of the air on cirof their deficiencies in one or more of the eleccuit breaking; its contacting surface is highly 6 trical or physical characteristics essential to wear resistant and is not readily pitted. good contact means. Besides having the aforementioned advan- An object of this invention is to provide contageous properties one of the salient advantages tact means especially adapted for use in high of my novel contact means is that the voltage duty electrical devices. drop across the contacts when in operative po- 70 Another object of my invention is to provide sition is relatively low so that the temperaturecontact means, the constituents of which perof the contact means per se is correspondingly mit them to be readily manufactured at a minlow to aid in maintaining the ambient air in the imum cost into units of substantially uniform atomic or molecular state rather than in an and unvarying dimensions. Y ionized state, thus aiding in quenching the are 75 Briefly the invention is directed to a novel when the circuit is broken at that station. contact means comprising generally a compos- In order thatthis contact means may be manite body consisting chiefly of a highly refractory ufactured in a simple and expeditious manner metal, such as tungsten, molybdenum or the I may employ the following initial products:

like, and a materially lesser refractory metal parts by weight of silver powder, all passing of ppr i y r a i al c nd ivity, a 200 mesh screen. 60 parts by weight of molybsuch as coppe v 0 t e e, ogether with denum powder, all passing a 150 mesh screen a relatively small proportion of a carbonaceous .5 to 4 parts by weight of powdered graphite, material, such as graphite. all passing a 200 mesh screen.

20 In the course of my experimentations with Any suitably sized charge is made up with th the manufacture and use of high electrical duty above constituents present in specified proporcontact means, I have found that by following tions. This charge is conveyed into the workthe method hereinafter outlined and by utilizing ing chamber of a ball mill of appropriate size from twenty to eighty per cent of the highly reand milled for about an hour. By this opera- 35 f ac y metal and eighty tK) enty per cent tion the constituents of the charge are intimately of the materially lesser refractory and appremixed with each other and are further pulciably higher electrically conductive metal, toverized. gether with a suitable proportion of carbonace- After the milling operation, the resulting th one aterial, such as graphite, ranging f oughly and intimately mixed powder is formed 40 two tenths of one per cent to ten per cent of the into units f the desired size and shape in any entire metallic constituents, comparatively inexsuitable manner such as by subjecting the i $$ty1 e s llg fi figifizy electncal dered mixture in an appropriate die to a pres- Although, by to owing the general method 51111:; of about one to twelve tons per square 45 hereinafter outlined, these materials maybe combined in any desired ratio within the above The thu,s fumed umts are then-heated specified limits, I will now describe one of the predetermleed temperajture' for a sumclent preferred specific embodiments of my invention length of tune as to msure a complete bond together with the novel method of producing ing of the partlcles and to develop a unitary 50 the same. structure having the desirable high electrical 5 The preferred contact means comprises a comduty characteristics essential to a contact means. posjte body which by weight consists of forty These results may be attained by heating the parts of silver, sixty parts of molybdenum and p e sed units i a yd atmosphere to a from one half to four parts of graphite. The pera ure o about to 1020 fOr a 55 contact means of this composition produced in period of about ten to thirty minutes. llO- The effect of this heat treatment is to fuse the silver to such a degree that it fills the interstices between the molybdenum particles-and between the molybdenum and graphite particles. When operating under these conditions, most-of the molybdenum, silver and graphite remains in their elemental form, with a small proportion of the silver and molybdenum alloying, and a small proportion of carbon uniting with the molybdenum to form a carbide.

The pressure and firing conditions may be varied depending on the degree of hardness de- The contact units so formed may be buifed or polished to any desired degree, if so desired, be-

fore mounting, but I have found that after a mere brushing operation they can be efliciently employed as high electrical duty contact means.

These units may be mounted in any convenient manner, as by means of stud bolts, to the appropriate contact supporting strip of a high electrical duty device. A

Having shown and described a specific embodiment oi my invention I do not desire to be limited thereto except in accordance with the appended claims.

What is claimed is:

An electrical contact including a composite unit comprising by weight about 60% molybdenum and 40% silver, the molybdenum and silver being uniformly distributed throughout substantially the entire mass, the molybdenum being in the form of individual particles and being surrounded by the silver. CHARLES v. IREDELL. v 

